Naloxone is an opioid antagonist, which rapidly reverses the effects of other opioids. Being a pure opioid antagonist, it has no euphoric or addictive pharmacological properties. Its primary mechanism of action is to competitively bind at opioid receptors, thus reversing the euphoric effects of other opioids such as heroin and oxycodone. Naloxone hydrochloride is prescribed under the trade name Narcan® and is primarily administered via injection for the immediate treatment of opioid overdose. Naloxone may also be combined with buprenorphine and prescribed as Suboxone. Administration of sublingual Suboxone doses of 8 mg/2 mg (buprenorphine/naloxone) yielded peak serum concentrations at 48 min. The half-life for naloxone is typically 1-3 hrs, while buprenorphine has a half-life of 33 hrs. Naloxone is primarily excreted in the urine as parent drug and glucuronide metabolite.
Currently, a selective immunoassay screen test for naloxone does not exist. Providers should be aware that naloxone may cross react with opiate and oxycodone immunoassay screen tests at higher concentrations. PremierTox Laboratory confirmation is performed via Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) with a low cut-off concentration of 2 ng/mL, and a reporting range up to 5000 ng/mL.
Patients in chronic suboxone therapy may be positive for buprenorphine and/or norbuprenorphine, as well as naloxone. The presence or absence of naloxone should be interpreted with clinical judgment, including consideration of dose, frequency and route of administration. A negative naloxone report may be the result of the lower naloxone dose compared to buprenorphine, and the longer half-life of buprenorphine (33 hrs) versus that of naloxone (< 3 hrs).
PremierTox provides naloxone adherence monitoring and confirmation of unexpected screen results using our state-of-the-art UPLC/MS/MS proprietary methodology. Naloxone confirmation may be ordered by itself or added to any confirmation group or panel, and is reported at a cutoff concentration as low as 2 ng/mL. Naloxone confirmation will be reported within 24-48 hours from specimen receipt.